This application claims priority under 35 U.S.C. xc2xa7xc2xa7 119 and/or 365 to 00-56152 filed in Republic of Korea on Sep. 25, 2000; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electron spectroscopic analyzer using X-rays and, more particularly, to an electron spectroscopic analyzer capable of increasing X-ray transmission efficiency and a signal to noise (S/N) ratio.
2. Description of the Related Art
Electron spectroscopic analyzers using X-rays have a variety of industrial applications. For instance, they are used for obtaining information about the atomic structures and arrays of electrons in atoms of industrially used materials such as semiconductor materials, catalysts and amorphous materials.
Currently used electron spectroscopic analyzers using X-rays are composed of an X-ray generator and an optical system which detects photo electrons emitted from an object onto which X-rays are radiated to analyze the object. However, in these electron spectroscopic analyzers using X-rays, since the optical system (in which the object to be irradiated with X-rays is positioned) is exposed to the air, X-rays generated by the X-ray generator are absorbed by particles in the air while traveling to the object. Particularly for soft X-rays, the absorption ratio of these particles in air is high, which makes the analysis of the intended object practically impossible.
A ratio at which soft X-rays are absorbed into particles in the air can be reduced by connecting an X-ray generator to an optical system using a vacuum system whose inside is maintained at a low pressure near to vacuum pressure. Here, X-rays are generated by bombarding an X-ray generative sample in the X-ray generator with accelerated electrons. However, during the generation of X-rays, electrons are emitted from the X-ray generator and incident on the optical system in addition to the photoelectrons generated by the object. As a result, a signal caused by electrons emitted from the X-ray generator is included in a signal containing information about the object. Accordingly, the S/N ratio is low.
To solve the above problems, it is an object of the present invention to provide an electron spectroscopic analyzer using X-rays, which is capable of accurately analyzing an object by increasing the X-ray transmission efficiency and increasing a signal to noise (S/N) ratio in an analysis signal containing information about the object at which X-rays are radiated.
To achieve the above object of the invention, there is provided an electron spectroscopic analyzer that includes an X-ray generator for generating X-rays, an optical system for detecting charged particles emitted from an object irradiated with the X-rays to analyze the object, a vacuum system whose inside is maintained at a low pressure near to vacuum pressure, the vacuum system being provided between the X-ray generator and the optical system, and a blocking unit provided between the X-ray generator and the optical system for preventing elements other than the X-rays emitted from the X-ray generator from flowing into the optical system.
Here, the blocking unit is provided within or outside the bellows. The blocking unit may be formed to surround the outside of the bellows. Alternatively, the blocking unit may be provided at the outer bottom of the bellows. The blocking unit may be provided at an inner portion of the vacuum system contacting the X-ray generator or an inner portion of the vacuum system contacting the optical system. The blocking unit provided outside the vacuum system may be a magnet.
The blocking unit provided at an inner portion of the vacuum system contacting the X-ray generator or at an inner portion of the vacuum system contacting the optical system may be a plate formed of a predetermined material which is transparent with respect to X-rays but is opaque with respect to elements other than X-rays emitted from the X-ray generator. The plate has a predetermined thickness. Here, the blocking unit may be selectively formed at only one of the inner portion of the vacuum system contacting the X-ray generator and the inner portion of the vacuum system contacting the optical system.
The blocking unit provided at the inner portion of the vacuum system contacting the optical system may be a plate which is transparent with respect to X-rays and other emitted elements and to which power is applied so that an electric field having the same characteristics as an electric field formed from other emitted elements can be formed within the bellows.
Alternatively, the blocking unit provided at the inner portion of the vacuum system contacting the optical system may have a center which is transparent with respect to X-rays and a shield around the center which is opaque with respect to X-rays. Power is applied to the blocking unit so that an electric field having the same characteristics as an electric field formed from the other emitted elements can be formed within the bellows.
A blocking unit provided at the inner portion of the vacuum system contacting the X-ray generator and/or a blocking unit provided at the inner portion of the vacuum system contacting the optical system may be implemented using a plate or plates thin enough to be transparent with respect to the X-rays and the other emitted elements from the X-ray generator. However, when the two blocking units are combined, a plate opaque with respect to the other emitted elements is formed.
The magnet may be an electromagnet and may be composed of at least two independent electromagnets.
The electron spectroscopic analyzer further includes a collector for collecting elements deflected by the magnet among the emitted elements other than the X-rays, the collector being integrated with the vacuum system between the magnet and the optical system.
Where the blocking unit provided at the inner portion of the vacuum system contacting the X-ray generator or the blocking unit provided at the inner portion of the bellow contacting the optical system is a plate which is transparent with respect to the X-rays and is partially transparent with respect to the emitted elements other than the X-rays, the other blocking unit is the shield.
The electron spectroscopic analyzer further includes a bottleneck portion provided in the middle of the vacuum system for preventing the other emitted elements from flowing into the optical system.
As described above, the present invention is provided with a vacuum system between an X-ray generator and an optical system and a blocking unit within or outside of the bellows. The blocking unit restrains or blocks inflow of elements other than X-rays emitted from the X-ray generator, particularly charged particles, to the optical system. Accordingly, the S/N ratio in a signal measured in the optical system can be increased, thereby increasing the accuracy of an object analysis. In addition, absorptivity of the X-rays can be reduced, thereby increasing the use efficiency of X-rays.